Process and device for form locked joining of two components

ABSTRACT

A process is described for form locking joining of two components through plastic deformation of one of the two components. In order for the tool for forming the form locking connection not to get in direct contact with the plasticized area of the joining partners, a third component between the tool and the two components to be joined through form locking is being used, which simultaneously enters into an adhesive bond with one of the two components to be joined through form locking. The thermal energy for creating the plastic state of one of the joining partners and for developing the adhesive bond is applied through electromagnetic radiation through the third component.

FIELD OF THE INVENTION

The invention relates to a process and a device for form locked joiningof two components and to a device for performing the process.

BACKGROUND OF THE INVENTION

In many mechatronic systems, e.g. in automotive sensorics, there is arequirement to integrate printed circuit boards into a housing. Sincethe electronics have to interface via connectors or other sensoricinterfaces with the system periphery, the printed circuit board has tobe fixated in the surrounding housing in a defined position. Foraccomplishing this object, a multitude of solutions is available in thestate of the art.

A possibility to establish disengageable connections is using threadedconnections. The disadvantage of this process is that the housing thenhas to be provided with a thread. When using plastic housings, athreaded metal insert is therefore often integrated during the injectionmolding process in order to obtain a load bearing thread. Consequently,manufacturing a respective connection is very expensive.

Among the non disengageable connection techniques, e.g. encasing theprinted circuit board in the housing or so-called hot caulking are beingused. During hot caulking, a rod shaped component, briefly also calledpin, is run through a hole in the printed circuit board, so that itrests on a shoulder. Subsequently, the pin protruding beyond thethickness of the printed circuit board is deformed under thermal energy,so that the pin forms a rivet head for form locked fixation of theprinted circuit board. A respective process using ultrasound energy forgenerating the necessary heat is described in DE 4215041 C3 (SiemensAG). A similar process is disclosed in JP 62064528 A (Toyota MotorCorp.), in which radiation energy is used to achieve the plastic stateof one of the joining partners. The hot caulking processes according tothe state of the art, however, have the disadvantage that forming therivet head is being performed through a contact tool. When using suchprocesses for hot caulking of plastic housings or printed circuitboards, this bears the risk of material sticking to the shaping tool.

Besides mounting the printed circuit board in the housing, also themedia tight closing of the housing is an important part of the valuecreation process of mechatronic systems. As a process which createsparticularly high quality welded connections, laser through transmissionwelding is industrially established. In this process, two joiningpartners, which can be welded through melting, are being combined, oneof which has a high degree of optical transmission for the wavelength ofthe welding laser that has been used, and however, the other joiningpartner strongly absorbs this wavelength. In an overlapping assembly ofboth joining partners, the welding radiation can transmit through thejoining partner facing it and is subsequently absorbed at the contactsurface of the two components. The absorbing joining partner is beingheated until both joining partners are melted in their contact areathrough heat conduction. In order to facilitate heat conduction betweenthe joining partners, these are loaded with a compressing force. Sincethe widely used plastic materials have low heat conductivity, theinduced welding energy remains in the joining zone for a certain periodof time, depending on how the process is performed, so that material,which is still soft, mostly from the absorbing joining partner can bedisplaced out of the joining plane under the influence of thecompression force. Under continued application of a compression force,the joining partners thus can perform a relative motion towards eachother, in order to compensate for possible gaps in the weld. Arespective process is disclosed e.g. in DE 102004004985 A1(Laserquipment AG). The process described therein, like other currentprocesses for closing housings, does not provide for a possibility tomount the enclosed printed circuit board, so that separate precursoryprocess steps are necessary, which is disadvantageous.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a reliable and errortolerant process for form locking connection of two components, whichdoes not have the disadvantages of the current state of the artprocesses. Furthermore, it is part of the object of the invention toperform the form locking connection of two components simultaneouslywith the adhesive bonding of a third component, in order to integratetwo process steps, and to thereby achieve a cost saving shortening ofthe process chain.

In order to achieve the object, it is suggested according to theinvention, to create the form locking connection between a first and asecond component through plastic deformations of the first component bya third component. The third component, thereby, does not have to be incontact with the second component, it is rather being used toplastically deform the first component, so that a form lockingconnection between the first and the second component can occur. Thethird component preferably enters into an adhesive bond with the firstcomponent, while establishing the form locking connection between thefirst and the second component.

The invention is characterized in that the plastic deformation toachieve form locking is generated through a third componentparticipating in the joining process, which by itself enters into anadhesive bond with one of the joining partners. A respective process isused e.g. for mounting printed circuit boards in a housing made fromthermoplastic plastic material.

The advantage of this procedure is that the tool, imparting the forcefor the plastic deformation, is not in direct contact with theplasticized component, so that an unwanted material adhesion on the toolcan be avoided. The invention thereby utilizes the state of the arttrough transmission welding process, in order to create the adhesivebond between the first and the third respective component, each weldablethrough melting, preferably made from thermoplastic plastic material,and to provide the energy to transform the first component into a state,where it can be plastically deformed. Furthermore, the invention ischaracterized in that, the first and the third component perform a feedmotion relative to each other under the influence of a compression forceduring the welding process, according to the explanations in the stateof the art, and that this feed motion is being used in order to producethe plastic deformation of the first component necessary for the formlocking connection of the first and second component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a portion of three components tobe connected to each other in a first process step according to a firstembodiment of the invention,

FIG. 2 is a schematic sectional view according to FIG. 1 in a secondprocess step, and

FIG. 3 is a schematic sectional view of three components to be connectedto each other according to a second embodiment of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

A first exemplary embodiment of the invention is illustrated in FIG. 1.The radiation absorbing joining partner (1) is depicted as a cutout,e.g. from an electronics housing. Through a pass-through hole (5) of thecomponent (2) to be connected in a form locking manner, e.g. a printedcircuit board, a column shaped riser (4), also called a pin, reachesthrough in the non joined state. An additional component (3) is placedonto this pin, initially in a loose manner, which is sufficientlytransparent for the imparted welding radiation (6). The radiationtransmitting component (3) has a concave cross section (7) in thecontact area with the pin, which supports the creation of the materialflow of the absorbing component (1) during the plastic deformation. Theradiation transmitting component is pressed down onto the pin (4)through a down holder (10) mounted coaxial with the welding radiation.After the pin (4) has been exposed to the welding radiation (6) for acertain amount of time, and has been imparted with the compression forcethrough the down holder (10), a plastic deformation of the pin (4) witha lateral material flow occurs, so that the assembly shown in FIG. 2 iscreated at the end of the process. During the joining process, materialof the pin (4) is plasticized through the heating of the weldingradiation, until it is displaced laterally under the influence of thecompression force, so that cooler material layers of the pin are exposedagain to the radiation and can be heated. Once the rate of materialdisplacement is in equilibrium with the rate of plasticization throughthe welding radiation, the down holder element (10) can perform aconstant feed motion in the direction of the absorbing joining partner(1). The concave indentation in the transmissive joining partner (7)supports the formation of the rivet head (8), necessary for the formlocking connection, during the feed motion by determining the flowdirection of the material. After a sufficient amount of material hasbeen displaced for forming the rivet head, the joining partner (2) to bejoined through form locking, is connected in a solid manner with theabsorbing joining partner (1). Since the pin (4) is made from laserabsorbing material, however, the initially loosely placed component (3)transmits the welding radiation (6), heat generation and adhesivelybonded welding finally occurs at the contact surface of the twocomponents.

A particularly advantageous embodiment of the process according to theinvention is shown in FIG. 3 before the joining process. Hereby, thetransmissive component, which produces the plastic deformation of thepin (4), is a component of the complete assembly at the same time, whichhas further functions besides creating form locking. Thus in the senseof this functional integration, e.g. the cover of an electronics housing(13), which is supposed to close the housing tight against media, cansimultaneously be used for forming the rivet head. Thereby, theradiation field of the welding radiation (6) is run along a welding bar(11), as described in the state of the art literature. The control meansof the device for performing the process allow that, besides the weldingbar (11), also the pin (4) is radiated within a short time interval fromthe radiation of the welding bar. Under the influence of the compressionforce, which is imparted along the circumferential welding rim with theassistance of a compression frame (12) onto the component cover (13) andthe welding rim (11), according to the process described in the state ofthe art, a feed motion of the compression frame (12) and the housingcover (13) occurs in the direction of the radiation absorbing joiningpartner (1). Through the alternating irradiation of the welding rim (11)and the pin (4), a plasticization of the pin (4) occurs, which can thenform the rivet head necessary for form locking through materialdisplacement, as described in the above embodiment. Between the weldingrim (11) and the housing cover (13), as well as between the pin and thehousing cover (13), an adhesive bond occurs, while a form lockingconnection was created between the pin (4) as a component of the lowerjoining partner (1), and the printed circuit board (2). The adhesivebond between the pin (4) and the housing cover (13) increases themechanical stiffness of the entire assembly, while the circumferentialweld closes the housing tight against media. It is particularlyadvantageous in this embodiment of the invention, that the process ofmedia tight welding is decoupled from the creation of the hot caulk withrespect to the geometric tolerances of the components. If the thirdcomponent (13) were directly used for form locking mounting of theprinted circuit board (2), typical manufacturing tolerances of thecomponents could cause the housing cover (13) to already make contactwith the printed circuit board, before the welding rim (11) has beenmelted down by the desired height. On the other hand, the welding rim(11) and the pin (4) could already be melted down by a predeterminedvalue, so that the entire joining process is terminated without theprinted circuit board (2) being firmly pressed against the lower joiningpartner (1). The creation of form locking according to the inventionthrough the displaced material of the pin (4) as a component of thelower joining partner, however, eliminates this problem.

REFERENCE NUMERALS

-   1 radiation absorbing joining partner-   2 joining partner to be connected through form locking-   3 radiation transmitting joining partner-   4 pin-   5 pass-through hole for pin-   6 welding radiation cone-   7 shape of rivet head in third joining partner-   8 plastically deformed pin (rivet head)-   9 area of adhesive bond joint-   10 down holder tool (punctiform)-   11 welding rim-   12 down holder tool (shaped according to contour of seam)-   13 housing cover

1. A process for form locking joining of two components, comprising thesteps of: positioning of a first and second component relative to eachother, which are to be joined through form locking, welding the first ofthe said components with a third component by a through transmissionwelding process, and loading the third component with a joining forceduring the through transmissions welding process, wherein through a feedmotion of the third component during the through transmission weldingprocess relative to the first component, material is displaced fromplastically deformable areas of the first component, so that thedisplaced material creates a form locking connection between the firstand the second component.
 2. The process according to claim 1, whereinduring the form locking joining process, in addition, areas of the firstand the third component are welded together by adhesive bonding, whoseplastic deformation does not create form locking with the secondcomponent.
 3. The process according to claim 1, wherein the first andthe third components are made from thermoplastic plastic material. 4.The process according to claim 1, wherein the first component is anelectronics housing, and the third component is a cover for thishousing.
 5. The process according to claim 1, wherein the secondcomponent is a printed circuit board.
 6. The process according to claim1, wherein a radiation used for plasticizing and welding the componentsis a laser radiation in a range of near infrared wavelength.
 7. Theprocess according to claim 1, wherein a radiation, which is used forplasticizing and welding the components, is a polychromatic radiation,generated by a halogen- or short arc lamp.
 8. A device for creating formlocking between a first and a second component, simultaneously creatingan adhesive bond of the first component with a third component,comprising: a radiation source for creating electromagnetic weldingradiation means for focusing the welding radiation into a weldingradiation field, means for positioning the welding radiation fieldrelative to the components to be joined, means for loading the first andthe third component with a joining force, which enabling a feed motion,and control means of the device enabling an alternating irradiation ofmaterial sections, which are to enter into an adhesive bond between thefirst and the third component, without creating form locking with thesecond component, and sections, which are to enter an adhesive bondbetween the first and the third component, and additionally a formlocking connection between the first and the second component throughplastic deformation.